Subdivided service system of radio broadcast distribution



Jurle '5, 1,9281 1,672,371

A E. E. CLEMENT SUBDIVIDED SERVICE SYSTEM OF RADIO BROADCASTDISTRIBUTION y i Filed Jilly 1924 2 Sheets-Sheet 1' June 5, 1928.

E. E. CLEMENT:

SUBDIVIDED SERVICE SYSTEM OF RADIO BROADCA S'I DISTRIBUTION Filed July9, 1924 2 Sheets-Sheet 2 {'23 9 8 I 1 P v czmmu. ornc: J" 2 1:. AND A.r.5

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UNITED STATES PATENT OFFICE.

EDWARD E. CLEMENT, OF WASHINGTON, DISTRICT OF COLUMBIA, ASSIGNOB TOEDWARD F. COLLADAY, OF WASHINGTON, DISTRICT OF COLUMBIA.

SUBDIVIDED SERVICE SYSTEM OF RADIO BROADCAST DISTRIBUTION.

Application filed July 9,

My invention relates to systems of radio broadcast distribution of thetype which I have designated b the name Radiowire, in which use is ma eof wired circuits, con- 5 neeting subscribers stations with a centralstation. It has for its object to simplify the subscribers radiophoneinstruments, and at the same time to extend the sec )e or range thereofas well as the power. Ot1er objects 1 are to unify and standardize theservice rendered, to permit supervision and control by operators at thecentral station of all lines and substation receiving, to give thecentral ofiice supervision and custody of the more delicate, com licatedand costly apparatus required in ong distance radio reception, to reducethe amount of such comlieated and costly apparatus, and to centralwe allhigh voltage and high power current supply apparatus. Other ob'ects willsuflicicntly appear from the detai ed description hereinafter.

I attain my ob'ects as follows:

I locate at each subscribers station a simple radio receiving set havinga wave collector, and a carrier wave transformer by means of which themodulated carrier waves received may be transformed into modulatedcarrier waves of.,difi'erent wave lengths suitable for line-radiotransmission to the central office. At the central ofiice I locate unitsfor receiving said line transmitted carrier waves, and for firstamplifying the same at radio frequency, then detecting and 85 amplifyingthe modulations at audio free quency and then transmitting the amplifiedaudio frequency waves back over the subscribers hne to his station wherethey are rendered audible by means of any suitable 0 telephone receivinginstrument.

l\ y invention is illustrated in the accompanying drawings, in which,

' Fig. 1 is a dia ram of a subscribers station, and a line circuitleading therefrom to a central station.

Fig. 2 is a diagram of cooperating circuits at the central station.

Figs. 3, 4 and 5 are diagrams of modifications of the apparatus at thecentral station.

Referring to the drawings in detail, and

first to Figs. 1 and 2, 1 and 2 represent a f subscribers telephone lineextending from 1924. Serial No. 725,086.

the subscribers station Fig. 1, to the central ofiice Fig. 2 where itterminates in line ternunal apparatus which may be of any known or othersuitable form indicated symbolically by the cut-off jack J. At thesubscribers station, Fig. 1, is provided the usual telephone instrumentTe arranged to be connected to the line 1-2 through conductors 3-4 andswitch Sw. A loud speaker L8 is also connected across the line 12 throuh switch 510' and conductors 5-6. The su scribers station is alsoprovided with a radio receiver S of the beat or heterodyne type whoseoutput terminals 7-8 are connected to the line wires 1-2. The inputconductors 18-19 of the subscribers radio receiver S are connected withthe loop antenna L which may be substituted by any suitable form of waveintercepting device. The subscribers receiver S consists generally ofthat portion of the well known superheterod ne receiver comprisin thefirst detector, osei la- 7'5 tor, and interme ate frequency or filtercoupler with a suitable current source. In this arrangement T is thefirst detector tube having the grid g connected to one of the inputterminals 19 throu h the grid con- 80. denser C and grid leak 9% and itsfilament f connected to the other input terminal 18 through the tappedcoupler coil 2' of an oscillator coupler I. The plate p of the firstdetector is connected to the lus terminal of 35 the B battery B throngconductor 12, coil i of the filter coupler I, and conductors 11 and 16the plate return circuit being by way of the connection of the filamentf through conductor 15 to the minus terminal of the B battery. Theoscillator tube T has its grid 9 connected through the coil 1'. of theoscillator coupled I to the filament f while its plate element p isconnected through coil 5 of the oscillator coupler and conductor 16 tothe plus terminal of the B battery, the plate return circuit being fromthe filament f throu h conductor 15 to the minus terminal of t e Bbatter The plate and grid terminals of the coils 1, and i are connectedthrough an oscillator tunin condenser C while the other terminals 0 thecoils i and i are connected through a fixed coupling condenser C. Thefilaments and f. are connected, as usual, through 05 suitable individualrheostats Rh and Rh across the terminal of the A battery A. by way ofconductors 14 and 15. The primary coil i of the filter coupler I isbridged by a condenser C of the proper capacity to form with the coil atuned circuit resonant at the desired beat or intermediate frequency asis usual in the filter coupler of the well known superhctcrodynecircuit. The arrangement of the secondary or output side of the filtercoupler I varies somewhat from the usual type in that the coil 11instead of being bridged by its tuning condenser C has this condenserconnected in series therewith and with the line so as to make the linepart of the resonant filter circuit, the condenser C being of thevariable type to afford sharp tuning.

At the central oflice, the connection of the line wires 12 is extendedthrough the normally closed contacts of the cut-off jack J to theconductors 2120 which connect with the terminal conductors 23-424 of afilter coupler I which forms the input coupling connection to thecentral otiice amplifier CO. This filter coupler comprises couplinginductance 11" and i with their tuning condensers C, and C",respectively, arran ed similarly to those of the filter coupler I of thesubscribers receiver and having substantially the same electricalconstants. The circuit of the central office amplifier CO from thefilter coupler I to the output jack J is the intermediate frequency andaudio frequency amplifier portion of the well known 8-tubesuperheterodyne, so that the system as shown in Fi s. 1 and 2 is inefiect a split, 8-tube superlieterodyne with the first detector andoscillator at the subscribers station connected over the line to theremainder of the circuit at the central ofiiee. The central otficeamplifier CO therefore consists of the usual three stages ofintermediate radio frequency amplification effected b the threeamplifier tubes T, T, and T etection effected by the detector tube T",and two stages of audio amplification efiected by the amplifier tubes T,and T", which several tubes are connected through suitable radiotransformers T1", T1, and Tr and audio transformers T1" and Tr. Theusual source of current at various potentials is provided in the form ofa stora e battery ta ped to form a filament or battery X, low voltage orconductor B battery B and high voltage or amplifier B battery Bconnected as usual in the filament circuits, second detector platecircuit and amplifier plate circuits, respectively. The voltage divider,or so-called potentiometer, P0 is provided in the grid return circuitsof the amplifier tubes T and T for the purpose of stabilizing the radiofrequenc stages, the filament return circuits being y-passed for radiofrequency currents around the voltage divider through conductor 28,by-pass eondenser C and conductor 25. The audio output jack J isconnected through a plug Pl and conductors 4142 to the line extensionconductors 2120, respectively for the purpose of )utt'ing the amplifiedaudio output from tie amplifier back on the subscribers line, the audiobeing blocked off from the input side of the amplifier by the lowcapacity condenser C which in the present instance is approximately.0002?) mi. As the plate voltage of the last amplifier tube T 90 volts,is much higher than that for which the ordinary telephone receiver isdesigned it is, of course, desirable to use astep down transformerbetween the line and the ordinary telephone receiver at the subscribersstation where this receiver is to be used in place of the loud speakerLs, although in practice it hasbeen found that very good reception canbe had on the ordinary telephone receiver R even with the loud speakerconnected across the line, reception of the loud speaker being nearlyall cut-ofi' due to the low resistance shown. It is also to be notedthat where desirable the loud speaker Ls may be designed to operate on alower voltage substantially the same as that of the regular receiver R,and the voltage transformation efiect'ed at the central otfice. It is tobe understood that suitable switches may be inserted in any of theconductors such as the line extensions 2120, input conductors 2322,battery leads, etc. for the purpose of throwing the circuits in and outof operative condition as is usual and well known in the art.

In operation, the subscriber may use his regular telephone forinitiating or receiving telephone calls over his telephone line 1-2 inthe usual way through the telephone exchange system, not shown. \Vhenthe subscriber at the substation Fig. 1 desires to receive radiobroadcast he secures, through the aid of the central ofiice o eratorsand supervisors, a connection with is line 12 through extension 2l20with the input and out ut terminals of a central ofiice amplifier 0 asindicated in Fig. 2, opens the switch Sw to disconnect his telephone setTe from the line and connects his loud speaker L8 to the line by closingthe switch S20 and adjusts the wave length condenser G and heterodyne oroscillator condenser C in the usual manner of operation of the wellknown superheterodyne set to produce with the desired wave a heat wavecorresponding to the wave length to which the filter cou lers I and Iand the line 1-2 are tune The long or intermediate freuency wave is thustransmitted over the hue 12 through the coupler I to the input side ofthe intermediate frequency and audio frequency amplifier CO at thecentral station, from which amplified audio output currents areconducted over the extension pair 41-42, line extension 21---20,normally closed contacts of cut-off jack J, subscriber 5 line 1--2 tothe subscribers loud speaker L by way of cord conductors 5-6. As all theadjustments of the amplifier C0 are fixed, the subscriber has control ofhis reception by the condensers C and C and by suitable adjustments ofsuch condensers may select any station within the radius of reception,the extent of-which range will be substantially the same as that of anS-tube superheterodyne set located wholly at the subscribers station. Itwill thus be seen that the subscribers apparatus is reduced to a verysimple form having but two tubes and no transformers, high potentialbatteries, or other of the more delicate and costly elements of the su)erheterodyne circuit, these latter elements being provided at thecentral ofiice where they may be readily repaired or replaced by expertswith little or no interruption to the subscribers service. It iscontemplated to provide interchangeable amplifier units CO at thecentral oflice which will thus render the subscribers receptionsubstantially roof against interruption as it has been ound in practicethat the weakest portion of a circuit of this type is the amphfiercircuit. It has also been found in practice that the detector andoscillator tubes at the subscribers station may be of a different typethan those at the central oilice and designed to work at a lowerfilament and plate voltage. For example, successful operation was hadwith two tubes of the U V199 type with but sixteen volts on the platecircuits of both tubes.

The manner of connecting the audio out.- put. of the central ofiiceamplifier to the line through a transformer is shown in Fig. 3 where Iindicates the audio transformer having its primary winding '5 connectedto the audio output conductor 41-42 and its secondary winding iconnected to the line extensions 2120. Otherwise the central otliceapparatus of Fig. 3 is the same as that of Fig. 2 and may be used insubstitution thereof with the subscribers line circuit and substationapparatus of Fig. 1. The arrangement of Fig. 3 has the advantage ofrendering the amplifier more stable in its action as well as affordingregulation of the mean voltage of the audio currents to that mostsuitable for transmission over telephone lines regardless of the voltageof the output currents of the amplifier which latter, in the presentstate of the art, usually requires relatively high voltages. Toreventleakage of direct current over the ine extensions 21-20 throughthe secondary i of the transformer, an audio condenser having a capacityof the order of 2 mi. may be connected in series with said winding.

The modified central ofiice circuit of Fig. 4 may be substituted forthat of Flg. 2 and is the same as it except that the subscribers lineextension has but a single wire connection with the input of theamplifier. This connection is made with the extension conductor 20through the conductor 43 to the closed primary circuit of the filtercoupler 1 In actual use, this circuit is found to give very clearreception with reliable stability in the action of the amplifier.

In Fig. 5 is shown a further modification of the central ofliceamplifier connection which may be substituted for that of Fig. 2 andwhich was found in actual tests to give very good reception at thesubscribefs loud speaker both as to clarity and volume. In hisarrangement the circuits are the same as that of Fig. 2 except thatthere is no physical coupling between the subscribefis line and. thefilter coupler I, the terminals of the primary circuit of the filtercoupler being connected with a twisted pair of insulated conductors. Inthe operation of this circuit it was found that reception wassubstantially unaffected by shortcircuiting the twisted pair 3031 ateither end.

As the purpose of the subscribers radio receiver of Fig. 1 is to receivebroadcast on the available wave lengths and to convert it into suitableform to be transmitted to the central ot'lice with the originalmodulations for amplification and detection, without interference withthe audio currents sent back to the subscriber, various other forms ofreceiving circuits capable of subserving this purpose may be used insubstitution thereof with the various central otiice amplifying circuitsdisclosed, for example, one tube may be saved in the subscribers receiver by delegating the functions of oscillator and detector to onetube by the use of the second harmonic as shown and described on page 59of the booklet entitled The Superheterodyne Manual by Victor Griefl",ublished by The Receptrad Press,

57 Bani: Street. New York city, copyrighted by Victor Griefl, 1924; thetwo tubes may be so connected that the first tube will act as a shortwave radio amplifier and the second one as a second harmonic oscillatorand detector, while by refiexing the first tube will also act as anintermediate frequency amplifier which circuit arrangement is shown anddescribed on page 60 of the publication just referred to; thesubscribers receiver may consist of a. long wave oscillator modu- 130lated by the incoming broadcast signal. or the broadcast may be of thedouble modulated type and the. subscriber's circuit comprise a detectorfor detecting an intermediate carrier of sufiiciently low fre uency tobe transmitted over the subscribers line to the central ofiice. Anothersystem which will enable the subscriber to receive broadcast I matter onshort wave lengths and convert the same into wave. lengths suitable foreflicient amplification at a distant point would be one similar to thatdisclosed in my copending application Serial No. 691,821, filed February9, 1924, in which, along with the broadcast matter, the subscriber isfurnished with a second wave, also by pure radio, and of a frequency toproduce with the first wave a heatwave of the desired frequency. \Vhilcin the disclosure referred to, no detector is shown at the subscribersstation, it is to be understood that a detector may be used there toeffect the detection or filtering out of the heat wave for trans missionover the line with the original modulations thereon, the line beingtuned to the beat frequency to act as the filter circuit of asuperheterorlyne system.

\Vhile I have herein illustrated and described certain specificembodiments of my invention for the purpose of disclosure, it is to beunderstood that the invention is not limited to such specificembodiments but contemplates all such modifications and variants thereofas fairly fall within the scqpe of the appended claims.

or example, the audio amplification or a portion of the amplificationmay be accomplished at the subscribers stat1on; all or portions of thetransmissions may be etlected over a single conductor or a plurality ofconductors used either in common or specialized, and various couplingarrangements may be used between the output and input of the centralizedamplifier circuit for regulating the input energy such as variousinductive, capacity, or resistance coupling means preferably capable ofvariation so as to effect a maximum of amplification without producingover regeneration or throwing the system into independent oscillation.

In its broadest aspect the principle involved in this invention is thatof collecting and transmitting waves at suitable frequencies from asubscribers station to a central station, there to be amplified andtransmitted back to affect responsive apparatus and thereby produceaudible sounds. In addition to the specific arrangement hereindisclosed, it is pointed out that when properly tuned the line may beregarded as a resonant circuit for any suitable frequency, or ifprovided with filters may be regarded as a suitable medium for thetransmissions of certain bands of frequencies whereby modulated wavesreceived at one station may be transmitted over the wires to anotherstation, may be amplified at said second station, and may beretransmitted to the first station at any suitable frequency within thetransmission range of the line. For example, by using the properso-called super-regenerat1ve arrangement to prevent injurious selfoscillation, the same fre uency may be transmitted both ways, as orexample the beat fre uency produced by heterodyning. In S1161 case, itwill of course be necessary to provide a second detector at thesubscribers station, or so arrange the circuits of the first detectorthat the waves amplified and reflected back from the central station maybe rectified and the audio modulations removed therefrom. 'Where thesame frequency is employed, as above stated, the line being tunedthereto, would constitute a resonant circuit excited at the first orsubscribers station and with the resonation amplified and derivingadditional energy or power from a source in the same circuit at thesecond or central station. Obviously then the oscillations would rise inthe line until suitably checked. due to the principle of regeneration.Such checking or chopping means, which divide the train of waves beingregenerated and amplified into groups or periods having a variationfrequency above that of audition, are well known in the so-callcdsuper-regenerative system of Armstrong and need not be described hereinin detail. It is also possible however to transform the frequency at thecentral ofiice before sending back the modulated waves to thesubscribers station, either to audio as herein specifically described,or to any other higher carrier frequency, i. e. above the limit ofaudition, that may be within the line transmission range. In party linepractice particularly, the application of the general principle claimedherein will involve the use of different carrier wave frequencies on thesame line, in order to render it pomible for different parties on thatline to receive different modulated wave trains at the same time. It isto be understood therefore,that all transmission back or forth in orover a line, tuned or untuned, of modulated wave trains, for the purposeherein set forth, is within the scope of this invention, as set forth inthe claims appended hereto. This would include the extreme case ofreception and detection of modulated carrier waves at a subscribersstation, and the transmission therefrom to central over the line wiresof audio waves, that is to say sound waves, to be amplified and sentback (in theory) over the line. As a matter of fact what would happen insuch a case would be the absorption of energy through the amplifyingmeans at the central station and the reimposition of the same currentchanges in phase, on the line, which in effect would be establishing acondition of negative resistance.

Having thus described my invention what I claim and desire to secure byLetters Patent is:

1. A radio receiving system comprising wave intercepting andtransmitting means, amplifying means and signal reccivin means, saidwave intercepting means and receiving means being -located at one point,and said amplifying means being located ata remote point with aconducting circuit connecting said intercepting means and amplifyingmeans tuned to the wave length of the current to be amplified andconnections over the same circuit from said amplifying means to saidreceiving means, with means to differentiate the intercepted waves astransmitted from the first point to the other or amplifying point, fromthe amplified waves at a different frequency retransmitted to theorginating point for audio reception thereat.

2. A radio receiving system comprising a primary receiving station and asecondary receiving station, a conducting circuit connecting saidstations, and means at the secondary station operating through oppositecurrents at different frequencies in said conducting circuit foramplifying signals received at the primary station, and retransmittingsaid amplified signals to the primary station.

3. A radio receiving system comprising a primary receiving station, anda secondary amplifying station, a conducting circuit connecting saidstations, means for producing two non-interfering currents between saidstations guided over said conducting circuit, means at the receivingstation for receiving and transmitting signals on one current to thesecondary station, and means at the' secondary station for amplifyingand retransmitting said signals on the other current back to the primarystation, with means to render said amplified signals audible in thereceiving apparatus of the receiving station.

4. A radio receiving system comprising a primary receiving station and asecondary receiving station, a conducting circuit connecting saidstations, means at the primary station for transforming direct currentinto a relatively low power carrier current, a source of current ofrelatively high power at the secondary station, means at the primarystation for receiving signals and retransmitting the same on the lowpower carrier current to the secondary station, and means at thesecondary station for amplifying said signals by means of the high powersource and retransmitting the same to the rimary station, saidtransmission over sai circuit in opposite directions being on differentfrequencies.

5. A radio receiving system comprising a primary receiving station, anda secondary receiving station, a conducting circuit connecting saidstations, means at the primary station for receiving and retransmittingsignals over the conducting circuit to the secondary station, and meansat the sec-- ondary station for amplifying and retransmitting'saidsignals over the said conducting circuit to the primar station, saidtransmission over said eircult in opposite directions being on differentfrequencies.

6. A radio receiving system comprising a primary receiving station and asecondary receiving station, a conducting circuit connecting saidstations, means at the primary station for receiving and retransmittingsignals over the conducting circuit to the secondary station onalternating current of a frequency at which the said conducting circuitis substantially resonant, a transformer-connected amplifying circuit atthe secondary station having transformers substantiall resonant to saidalternating current and connected to receive and amplify saidalternating current, means at the secondary station for detecting thesignals from the amplified alternating current, and means for amplifyingand transmitting said signals by direct current over the conductingcircuit to the primary station.

7. A radio receiving system comprising a primary receiving station and asecondary receiving station, a conducting circuit connecting saidstations, means at the primarv station for receiving and transmittingsigna over said conducting circuit to the secondary station atrelatively low ower, and means at the secondary station orretransmitting said signals over the conducting circuit to the primarystation at relatively high power, said transmission over said circuit inopposite directions being on different frequencies.

8. A radio receiving system comprising a primary receiving station and asecondary receiving station, a conducting circuit connecting saidstations, radio receiving apparatus at the primary station comprisingthe heterodyning and filter coupler portion of a superheterodynereceiving set, having the secondary element of its filter couplerconnected to the conducting circuit, amplifying apparatus atthesecondary station comprising the intermediate frequency amplificationand audio amplification portion of a superheterodyne circuit having itsinput end connected to the conducting circuit through a filter couplerand its output circuit connected to the conducting circuit independentlyof the said filter cou ler, and telephone receiving means at t 1eprimary station connected to the conducting circuit.

9. A radio receiving system comprising in combination with a telephoneexchan e system having a central office and su scribers substationsconnected therewith over telephone lines, a subscribers superheterodynereceiving set arranged with the receivingand heterodyning portion at the.subscribers station and the amplifying portion at the central office,said portions being operatively connected through the subscribers line,a filter coupler connected between said receiving and heterodyningporfrom that to which the tuned, and receiving means at the subscribersstation adapted to reproduce said signals.

In testimony whereof I hereunto affix my signature.

EDWARD E. CLEMENT.

lter coupler is 12, Ara 7 2 0 3 5

